Electromagnetic device and method of making same



0. E. ANDRUS July 31, 1951 ELECTROMAGNETIC DEVICE AND METHOD OF MAKINGSAME Filed Jan. 21, 1948 2 Sheets-Sheet l INVENTOR Orrm E. Andrus %ZMATTORNEYZ 0. E. ANDRUS ELECTROMAGNETIC DEVICE AND METHOD OF MAKING SAMEFiled Jan. 21. 1948 2 Sheets-Sheet 2 ATTORNEY.

INVENTOR. Orr-m E. Andru W40. 46%

Patented July 31, 1951 ELECTROMAGNETIC DEVICE AND METHOD OF MAKING SAMEOrrin E. Andrus, Altadena, CaliL, assignor to A. 0.

Smith Corporation, Milwaukee, Wis., a corporation of New YorkApplication January 21, 1948, Serial No. 3,384

2 Claims. (Cl. 171-252) This invention relates to an electromagneticdevice such as a motor stator and the method of making same.

The steel, copper, varnish, paper and slot sticks in electromagneticapparatus, such as a motor stator have different thermal coefficients ofexpansion. In large motors, in particular, the differences in expansionof the various parts is appreciable and the copper coils tend to movewith respect to the core. The insulation under these conditions islikely to crack and separate causing electrical breakdown and failure.

One object of the invention is to remedy the described condition byproviding a stator or other electromagnetic apparatus in which thelaminations are twisted or offset and the windings bound thereto and toeach other so that the laminations and windings move as a unit.

Another object is to provide a stator in which the laminations aretwisted and held in a crimped state by welding.

Another object is to provide a method of constructing a twisted motorwinding to prevent injury to insulation by differences in theexpansionand contraction of the parts.

Another object is to provide a stator in which the laminations andwindings are bound together in such a manner that there is no greatmovement of one with respect to the other in a single area which wouldproduce failure of insulation.

A further object is to bind the windings within the laminations toprevent injury to the windings by chaffing from vibration.

Other objects and advantages of the invention will appear hereinafter inconnection with the following description of several embodiments of theinvention illustrated in the accompanying drawing in which:

Figure l is a perspective view of a stator before twisting;

Fig. 2 is a fragmentary transverse section through the stator withwindings assembled therein and ready for twisting;

Fig. 3 is a sectional view of a stator confined in clamping diespreparatory to twisting the same;

Fig. 4 is a view showing the method of welding the stator aftertwisting;

Fig. 5 is a perspective view showing a stator after twisting; and

Fig. 6 is a view similar to Fig. 5 showing the stator twisted in anothermanner.

The invention is illustrated by the stator I formed of a plurality ofstacked laminations 2 having slots 3 to receive the windings 4. The

slots 3 are lined with a suitable insulating material 5, such as paperor the like.

The windings may be assembled in slots 3 in a number of different ways.They may, for example, be preformed and inserted in the slots as a unitor the individual conductors may be progressively introduced into theslots. Ordinarily the parting strip 6 is provided in each slot to lessenthe voltage differences between the conductors of the windings.

The insulating material 5 is preferably lapped at the mouth of each slot3 to enclose windings 4 within the slots and slot stick I of softnonmagnetic metal or synthetic material is located in the longitudinalgroove 8 adjacent the mouth of each slot 3 to close the slot and holdthe windings in place.

The laminations 2 of stator l are twisted or offset axially with respectto each other and the windings 4 are bound within, the laminations inthe twisting operation, as will be described more fully hereinafter.

The laminations 2 are held in a twisted state by a plurality of welds 9which extend the length of the stator. Mechanical means, however, mayalso be employed to hold the laminations after twisting is accomplished.

In carrying out the invention the laminations 2 are first stackedtogether with slots 3 in longitudinal alignment. Thereafter the slotsare lined with insulating material 5 and the windings 4 are insertedwith the parting strip 8 being disposed midway of each slot to separatethe conductors. The insulating material 5 is then lapped at the mouth ofthe slot and each slot stick 1 is slipped into its respective groove 8.

The twisting of the stator can be accomplished in a number of differentways and the twist or offset of the laminations 2 may take severalforms. Thus the stator may be twisted along the entire length or theslots merely arched in a single arc. Figs. 5 and 6 show a slot of thestator after twisting and illustrate several embodiments of theinvention.

Fig. 3 illustrates apparatus for twisting laminations 2. In carrying outthe twisting operation, after assembly of the windings 4 and laminations2 of the stator I, the mandrel I0 is inserted through the air gap of thestator and nuts I I are threaded onto the ends of the mandrel andagainst spacer members engaging the outermost laminations 2. The nutsll, however, are not initially tightened in place.

The entire assembly is then placed in a fixture comprising split clampsI2 at each end and which are supported on a base member II. The splitclam'p I4 is assembled around the center of the stator I. The clamp IIis rotatable and is rotated by handle IS. The clamps I2 and clamp I4 aresecured around the stator by suitable bolts. When handle I! of centerclamp I4 is grasped and pushed or pulled by the operator the clamps I2securely hold the stator at either end and the laminations 2 are twistedor ofl'set as desired.

The oflset or twisting of the laminations to bind or pinch the windings4 within intimate contact with themselves and with the laminations 2should be suflicient to force the windings 4 and laminations 2 to expandand contract as a unit.

After twisting the laminations 2, as described, the nuts II aretightened securely against the spacers engaging the laminations, thestator I is then removed from the clamps I2 and clamp ll of the twistingfixture, and the laminations 2 are permanently joined together in thetwisted state by longitudinal electric arc welds Q or other suitablemeans.

It is preferable. however, to join the laminations together by welds 8.In carrying out the welding operation it is necessary to prevent thewelding heat from penetrating to windings I and injuring the same.

The stator I, still retained in a twisted condition upon mandrel II bynuts II, after removal from the twisting dies, is placed in tank I6, onV- shaped support I'I. Tank I6 is filled with water up to a line whereonly the upper longitudinal portion of the laminations I of the stator Iare exposed.

The welds 9 are then made by depositing weld metal along the length ofthe laminations by a welding rod I8 which is connected to a weldinggenerator, not shown, through cable I8. Fig. 4 illustrates how one ofthe longitudinal welds 8 is made. When one weld is made, the stator I isrotated to another position by the operator and another weld 9 is thenmade along the longitudinally exposed portion oi. the stator. The waterin tank I6 carries away the heat of the arc and prevents the windingsfrom being burned.

After the welding is completed the stator I is lifted from the tank I8,the nuts II are unthreaded and the stator is removed from mandrel II).

The stator may be completed by being dried, impregnated with varnish andbaked.

Under the invention, the laminations and windings expand and contractsubstantially as a unit and there is no tendency of the windings toslide in and out of slots 3 in service. Strain on the varnish insulationis held at a minimum and breaking thereof which would ordinarily occurif the windings were free to move away from and through the laminationsis prevented. The tightness and the crookedness of the windings 4throughout the length of the entire stator insure that there will be noseparate movement with respect to the laminations and the windings.

The insulating material 5 separating windings I from laminations 2prevents damage to the windings when the latter are bound tightly withinthe laminations. The material 5 also stretches to some extent in serviceto take up minor difterences in expansibility between the ironlaminations 2 and copper windings 4.

Where the twisted stator is employed it is unnecessary to twist therotor bars of the rotor with which the stator is used. Inaddition thewinding coils are assembled more readily since the mouth or the slotsmay be initially wider for assembling the coils as the twisting of thecore narrows the mouth of the slots in the final core.

Various embodiments of the invention may be employed within the scope ofthe accompanying claims.

I claim:

1. A twisted laminated core having the corresponding slots of thelaminations thereof oiiset from each other, motor windings disposed insaid slots before oilset thereof and bound within said core by oflsetoi! the laminations to eflect substantially unitary movement of thelaminations of the core and the windings under thermal expansion andcontraction in service, and a longitudinally extending member separatefrom said windings and securing sa d laminations in offset relation.

2. A twisted laminated core having longitudinal slots extending throughthe laminations of the core with the corresponding slots of individuallaminations oifset circumferentially in the core, motor windingsdisposed in said slots before offset thereof and bound in intimatecontact with said laminations and with each other by offset of thelaminations to provide for substantially unitary movement of thelaminations and windings under thermal expansion and contraction inservice, and an interlock between said laminations to secure the same inoflset relation.

ORRIN E. ANDRUS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,150,049 Martin Aug. 17, 19152,012,021 Petersen Aug. 20, 1935 2,248,167 Elsey July 8, 1941 2,386,138Rancher Oct. 2, 1945 2,448,785 Dolan Sept. 7, 1948 FOREIGN PATENTSNumber Country Date 167,285 Switzerland May 1, 1934

